Core practicals Flashcards
What is the test for glucose?
The test for glucose involves adding Benedict’s solution to a sample in a test tube and heating it in a water bath at 60 to 70°C for 5 minutes A positive test shows a color change from blue to orange or brick red
What is the test for starch?
The test for starch involves adding drops of iodine solution to a food sample A positive test shows a color change from brown to blue black
What is the test for protein?
The test for protein involves adding drops of Biuret solution to a food sample A positive test shows a color change from blue to purple
What is the test for lipid?
The test for lipid involves mixing the food sample with ethanol then adding to an equal volume of cold water A positive test shows a cloudy emulsion
How can enzyme activity be affected by changes in temperature?
To test enzyme activity starch solution is heated to a set temperature and iodine is added to wells of a spotting tile Amylase is added to the starch solution and mixed Every minute a droplet is added to a new well with iodine until it no longer turns blue black The time taken is recorded and repeated at different temperatures
How can enzyme activity be affected by changes in pH?
To test enzyme activity with pH iodine is added to wells of a spotting tile and amylase is mixed with buffer solution and starch Every 10 seconds a drop is tested in iodine until it no longer turns blue black The time taken is recorded and repeated with different pH values
How can diffusion be investigated in a non living system?
Diffusion can be investigated by placing agar jelly with phenolphthalein and sodium hydroxide in dilute hydrochloric acid The jelly turns colourless as acid diffuses into it and neutralises the base
How can osmosis be investigated in a non living system?
Osmosis can be investigated by placing a Visking tubing bag filled with sucrose solution into a beaker of water Water moves into the bag through the partially permeable membrane causing the level in the capillary tube to rise
How can osmosis be investigated in a living system?
Osmosis can be investigated by placing potato cylinders in water and sucrose solutions of different concentrations Measure their mass or length before and after 30 minutes to see the change
How do you calculate the amount of energy in food?
Burn a food sample under a boiling tube containing water Record the starting and final temperatures Use the equation energy transferred equals mass times 4.2 times change in temperature divided by the mass of food
How can you investigate the need for chlorophyll in photosynthesis?
Place a leaf in boiling water then hot ethanol then water again Add iodine solution to test for starch Blue black areas indicate photosynthesis only where chlorophyll is present
How can photosynthesis be investigated using a water plant?
Use Elodea and count the bubbles of oxygen released from the cut end over one minute More bubbles means a faster rate of photosynthesis
How can the evolution of carbon dioxide in respiration be investigated?
Place germinating seeds boiled seeds and glass beads in separate tubes with hydrogen carbonate indicator A colour change indicates carbon dioxide production
How can the evolution of heat in respiration be investigated?
Place germinating seeds in one thermos flask and boiled seeds in another Use thermometers wrapped in cotton wool to measure temperature change over time
How can the effect of light on net gas exchange be investigated?
Place a plant in a beaker of hydrogen carbonate indicator and set a lamp at different distances Record the colour of the indicator to determine carbon dioxide levels
What should you use to collect a volume of gas?
A gas syringe should be used to collect a volume of gas
How can carbon dioxide in exhaled air be investigated?
Blow into limewater through a straw and observe the solution turning cloudy which shows carbon dioxide is present
How can the effect of exercise on breathing be investigated?
Count the number of breaths taken in one minute before and after exercise Repeating and averaging results shows that breathing rate increases with exercise
How can environmental factors affect transpiration rate?
Use a potometer to measure how far an air bubble moves in a capillary tube with a leafy shoot under different conditions Greater distance means faster transpiration
How can the conditions for germination be investigated?
Place cress seeds in four test tubes with different combinations of water oxygen and temperature Observe which tube has the most germinated seeds
How can carbon dioxide production by yeast be investigated?
Mix yeast with sugar solution and cover with oil Connect to limewater using a capillary tube Count bubbles produced at different temperatures to find the rate of respiration
